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Fly River

geography Maturity 7-9 Next article →

The Fly River is a massive and powerful waterway located on the island of New Guinea.

Flyriver
Flyriver

It sits in the southwest of Papua New Guinea and the South Papua province of Indonesia. The river is the third longest on the island, following the Sepik and Mamberamo rivers. It is also the largest river in Oceania by volume of discharge. Remarkably, it is the largest river in the world without a single dam in its catchment area. This makes it the 23rd-largest primary river in the world by discharge volume.

The river system begins high in the mountains. It rises in the Victor Emanuel Range, which is part of the Star Mountains. From these heights, the water flows down through the southwestern lowlands. Eventually, the river reaches the Gulf of Papua, where it forms a large delta. The Fly–Strickland River system is particularly significant. It is the longest river system found on any island in the world. The Strickland River is the largest tributary of the Fly. It also serves as the farthest distance source for the river system.

The river's path also serves as a political boundary. For a small stretch, the Fly River forms the international border between Papua New Guinea and Indonesia. This section moves slightly west of the 141°E longitude line. To balance this, the border south of the river sits slightly east of that same line. As part of this territorial arrangement, Indonesia has the right to use the river for navigation all the way to its mouth. The river is fed by several major tributaries, including the Strickland and the Ok Tedi.

Near the mouth of the river, a unique natural phenomenon occurs. The flow of the Fly River encounters a tidal bore. This happens when an incoming high tide pushes seawater upstream against the river's flow. This process continues until the tide changes direction. While this is a powerful event, the exact range of this tidal bore remains undocumented. The river's discharge levels vary greatly depending on the location and time. For example, at the Ogwa station, discharge can range from 2,201 m3/s to 18,214 m3/s.

The Fly River Delta is a world-class example of a tide-dominated delta.

Fly River Delta-txu-oclc-6552576-sc54-4
Fly River Delta-txu-oclc-6552576-sc54-4

Geologists use this delta as a "type case" or a model to understand ancient rock records. The delta has a distinctive funnel shape in plan view. This shape is caused by the fundamental role of tidal currents in shaping the land. At its entrance, the delta is over 100 km wide. However, it is only 11 km wide at the apex upstream of Kiwai Island. The delta contains three main distributary channels: the Southern, Northern, and Far Northern Entrances.

These channels are between 5 and 15 meters deep. They are separated by long islands made of sand and mud. These islands are stabilized by thick mangrove vegetation. In the apex area, the islands are constantly changing. They erode and rebuild rapidly, with lateral migration rates reaching up to 150 m/a. The delta is also home to many people and unique wildlife. The islands are flat and covered in fertile alluvial soil. Inhabitants engage in hunting and agriculture, growing crops like sago palm, breadfruit, and sugar cane. One notable resident is the Fly River turtle.

Flyriver
Flyriver

Also called the Pig-nosed turtle, it is the only freshwater turtle with flippers.

European history with the river began in 1845. Francis Blackwood discovered the river while commanding the corvette HMS Fly. The river was named after his ship. Later, in 1876, the Italian explorer Luigi D'Albertis attempted to travel deep into the interior.

Fly River Map 1876 NLA
Fly River Map 1876 NLA

He used a steamer named Neva and traveled 900 km inland. This was the furthest any European explorer had reached on the island at that time. His original survey map is still used to study the area today.

Today, the river system faces significant environmental challenges. The Strickland and Ok Tedi Rivers are sources of environmental controversy. This is due to tailings waste from the Porgera and Ok Tedi mines. Tailings are the materials left over after processing ore. In 2008, an advisor claimed that parts of the Fly River floodplain face risks from acid mine drainage. This occurs when minerals in the waste react with water to create acid. While some studies in 1994 found no high copper concentrations in the delta, the impact of mining remains a serious topic of study.

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File:Flyriver.png
Flyriver.png
File:Fly River Map 1876 NLA.jpg
Fly River Map 1876 NLA.jpg
File:Fly River Delta-txu-oclc-6552576-sc54-4.jpg
Fly River Delta-txu-oclc-6552576-sc54-4.jpg
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